Using PowerShell to identify a machine as a server or PC - powershell

Question

I'm trying to write a PowerShell script that will give me a list if of roles and features if run on a server but if run on a client machine will say "Only able to execute command on a server."
I've played around with this script a lot and can get it to run on either a client machine or server (depending on what I've tweaked) but not both. Here's the latest iteration:
$MyOS="wmic os get Caption"
if("$MyOS -contains *Server*") {
Get-WindowsFeature | Where-Object {$_. installstate -eq "installed"
}}else{
echo "Only able to execute command on a server."}
What am I doing wrong?

Answer 1

The quotes around your wmic command will create the $MyOS variable with a String and not execute the command. Still, I would recommend you use native PowerShell commands such as Get-CimInstance. Like the $MyOS variable your if statement condition will always equal true as the quotes will make it a String.
$MyOS = Get-CimInstance Win32_OperatingSystem
if ($MyOS.Caption -like "*Server*") {
Get-WindowsFeature | Where-Object { $_. installstate -eq "installed" }
}
else {
Write-Output "Only able to execute command on a server."
}

Answer 2

You can also use the ProductType property. This is a (UInt32) number with the following values:
1 - Work Station
2 - Domain Controller
3 - Server
$MyOS = (Get-CimInstance Win32_OperatingSystem).ProductType
if ($MyOS -gt 1) {
Get-WindowsFeature | Where-Object { $_. InstallState -eq "installed" }
}
else {
Write-Output "Only able to execute command on a server."
}

Answer 3

Try to use '-like' instead of 'contains', it should work

Answer 4

Generally, I try to avoid pre-checks like this that make assumptions about functionality that may not be true forever. There's no guarantee that Get-WindowsFeature won't start working on client OSes in a future update.
I prefer to just trap errors and proceed accordingly. Unfortunately, this particular command produces a generic Exception rather than a more specifically typed exception. So you can't really do much other than string matching on the error message to verify specifically what happened. But there's very little that can go wrong with this command other than the client OS error. So it's pretty safe to just assume what went wrong if it throws the exception.
try {
Get-WindowsFeature | Where-Object { $_. InstallState -eq "installed" }
} catch {
Write-Warning "Only able to execute command on a server."
}
If you don't want to accidentally hide an error that's not the client OS one, change the warning message to just use the actual text from the error. This also gets you free localization if you happen to be running this code in a location with a different language than your own.
Write-Warning $_.Exception.Message